A ball valve for process systems has a field-adjustable CV number. The CV number allows the valve to be “tuned” for its system. The ball, controlled by an actuator, is moved 0–90 degrees. An adjustable V-port then adjusts the CV number.
The upstream seat of the valve is modified with a movable shield so that it covers or exposes the opening in the ball. A shaft that passes through the wall of the valve allows the shield to be adjusted from the outside by a knob or other device. No replacement of the shield or any other part of the valve is required. The adjustable CV number can be tuned so the control valve is required to operate 0–100% when the load goes from low to high.